In computer science, a bitrate is a volume of information per second. As the unit of information is the bit (0 or 1), the bitrate is expressed in kilobits per second, shortened in kbps. It is worth noting (for one’s education!) that the multiplying prefix “kilo” (designated with the symbol “k”) is here worth 1,024, and not 1,000. Indeed, there is a frequent use of the powers of 2 in computer science, and 1,024 is 1,000’s closest power of 2, specifically 2 to the tenth power. Likewise, the prefix “Mega” (“M”) is worth 1,048,576, i.e. 2 to the twentieth power, 1,000,000’s closest power of 2. It is also good to know that if a bit is represented by a lower-case b, a capital B stands for byte, a unit worth 8 bits (called an octet internationally, represented by an “o”).
So, B = byte = octet = o = 8 bits. We’ll also note that the Internet bandwidth is usually expressed in Mbit/s, i.e. approximately 1,000 kbps, to keep our numbering system consistent.
Let’s talk now about the bitrate of the Hi-Res albums you can stream with the Qobuz Sublime+ subscription. The bitrate of an audio file is calculated as follows: Sampling rate (S/s, or samples per second) x number of bits (16 or 24) x number of channels (2 in stereo)
For Hi-Res files, you get:
- 24 bits at 44.1 kHz, bitrate = 2,116 kbps
- 24 bits at 48 kHz, bitrate = 2,304 kbps
- 24 bits at 88.2 kHz, bitrate = 4,233 kbps
- 24 bits at 96 kHz, bitrate = 4,608 kbps
- 24 bits at 176.4 kHz, bitrate = 8,467 kbps
- 24 bits at 192 kHz, bitrate = 9,216 kbps
For the record, the bitrate of a CD quality file (16 bits at 44.1 kHz) is equal to 1,411 kbps. But these bitrates values are for uncompressed files (i.e. « peak » bitrates, which correspond to the entirety of the digital audio stream) or for lossless files (whose compression will allow the original data to be perfectly reconstructed after decompression)—as is the case for audio files streamed from Qobuz that are compressed in FLAC (Free Lossless Audio Codec) before being broadcast on the Internet.
In order to know the bitrates of Hi-Res files after a FLAC compression, we used the Foobar2000 audio player software, which indicates the bitrate of the files during playback, even compressed ones.
Below are the results that we have obtained with the FLAC files used for our tests:
- 24 bits at 44.1 kHz, bitrate = 1,564 kbps
- 24 bits at 48 kHz, bitrate = 1,018 kbps
- 24 bits at 88.2 kHz, bitrate = 2,485 kbps
- 24 bits at 96 kHz, bitrate = 3,129 kbps
- 24 bits at 176.4 kHz, bitrate = 4,769 kbps
- 24 bits at 192 kHz, bitrate = 6,971 kbps
However, these numbers are only indicative, the compression rate depending of the frequency and dynamic range of the compressed music (FLAC encoding is “smart” and adapts itself to the original file). We should also note in the results above that the bitrate of the compressed 24 bit/44.1 kHz file is higher than the bitrate of the compressed 24 bit/48 kHz file. The first track, Defiant Order, from the eponymous album by Birdy Nam Nam, is rich in bass at loud volume. It relays a large volume of information, especially in dynamic range, which won’t be compressed much. Whereas the second track, the Turkish March from Mozart’s
Furthermore, because your Internet connection won’t be used exclusively to stream Qobuz files, we believe it is prudent to aim for a faster connection—especially if you want to stream 24 bit/192 kHz files.
If you are a manufacturer, importer, retailer or key player in the digital music industry and wish to contact us, you can do so using the following email address:newstech@qobuz.com
If you’re enthusiastic about the Hi-Fi Guide column and wish to contact us, you can do so using the following email address: rubriquehifi@qobuz.com
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